Optical element and method for the production thereof

ABSTRACT

Described is an optical element for guiding electromagnetic radiation. The optical element includes a base body and at least one film, wherein the film is configured to adhere to the base body to form an intimate connection with the base body without using an adhesion promoting interlayer and is arranged such that the electromagnetic radiation passes through it.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional and claims the benefit of U.S. patentapplication Ser. No. 11/815,030, filed on Mar. 20, 2008, which is thenational stage of International Patent Application PCT/DE2006/000081,filed on Jan. 19, 2006, which claims priority to German PatentApplication 10 2005004447.6, filed on Jan. 31, 2005, and German PatentApplication 10 2005006635.6, filed on Feb. 14, 2005. The contents of theabove applications are herein incorporated by reference in theirentireties.

TECHNICAL FIELD

The invention relates to an optical element and a method for theproduction thereof.

BACKGROUND

A device for diffusely illuminating transparent surfaces or bodies isknown from Patent Application DE 44 04 425 A1. To obtain good diffuseillumination even with weak light sources, the device comprises at leastone light source that is disposed at a core of the device and emanateslight inward into the interior. A partially transparent layer and an atleast partially reflective layer are disposed on the core.

SUMMARY

Objects of the present invention are to specify an optical element thatcan be used in a particularly varied manner and a method for theproduction thereof.

An optical element according to the invention, which is preferablyconfigured to guide monochromatic or polychromatic electromagneticradiation, comprises a base body and at least one film. The film adheresin intimate connection to the base body and is arranged such that theelectromagnetic radiation passes through it.

Such an optical element for guiding electromagnetic radiation,particularly preferably in the visible range, can be composed of a basebody and a film.

The radiation guided through the optical element impinges on a radiationentrance face and on a radiation exit face. The radiation exit face canbe arranged parallel or perpendicular to the radiation entrance face.Both faces are part of the surface of the optical element.

The base body is advantageously formed of a transparent material.Examples of usable transparent materials that are radiation-transparentand do not scatter radiation are epoxy resins, acrylic resins, siliconeresins or mixtures of these resins. However, the base body can alsocomprise an optically active material. An optically active material can,for example, contain particles serving to convert the radiation intoradiation of another wavelength or to effect scattering.

The geometrical shape of the base body can be suited to the intended useof the optical element, and can, for example, be plate-shaped orlens-shaped.

Particularly preferably, the base body is configured as a waveguide orlens, and in combination with the film is suitable, for example, foruniformly backlighting a display device, for example an LCD, or forshaping the radiation.

The film preferably adheres in intimate connection to the surface of thebase body without any need for an adhesion-promoting interlayer, forexample a glue.

The film can be located on various sides of the base body. One option isto dispose the film on the side occupied by the radiation exit face ofthe optical element, such as a lens, for example. Another option is todispose the film on the side occupied by the radiation entrance face ofthe optical element, such as a lens, for example. A further option is todispose the film, not on the respective sides occupied by the radiationentrance or exit faces of the optical element, but on one or more of theother lateral faces; this can be suitable particularly in the case of anoptical element in the form of a waveguide.

The radiation guided through the base body preferably passes through thefilm. In this case it has proven advantageous to use transparent ortranslucent materials for the film. Translucent materials, unliketransparent materials, can at least partially scatter the radiation.

Furthermore, the film can be an optically active film, which means thatproperties of the radiation are altered by the film. For example, theshaping, the wavelength or the intensity of the radiation can beinfluenced. A combination of influences on these variables may also becontemplated. By contrast, a film is considered to be optically inactiveif the radiation merely passes through it unaffected, apart from anegligible displacement of the beam.

For example, the shaping of the radiation can be influenced by means ofparticles in the film that scatter the radiation. Furthermore, a filmhaving a structure can be used to obtain a lens effect.

The film preferably contains phosphors to convert the radiation intoradiation of another wavelength.

In a preferred embodiment, the film is disposed on the side occupied bythe radiation exit face of the optical element. With this type ofarrangement, it is possible to influence the shaping of the radiationextracted from the optical element, for example through the use of apartially transparent film having a structure.

The intimate connection between the film and the base body has in thiscase proven particularly advantageous for the intensity of the extractedradiation. This is because an intimate connection, as opposed tomechanical mounting of the film, avoids the formation of an air gap,thereby reducing radiation losses and total reflection.

In a further embodiment, the film is disposed on one or more sides ofthe optical element, and specifically where neither the radiationentrance face nor the radiation exit face is located.

The film can be transparent or translucent. Disposed after the film isanother film, preferably a reflector film. It is also conceivable for aplurality of additional films, for instance in the form of a film stack,to be disposed after the film.

An air gap is formed between the film and the reflector film in thiscase.

Radiation fractions whose angle of incidence (relative to the surfacenormal) is greater than the angle of total reflection are advantageouslytotally reflected at the transition from the film, the optically densermedium, to the environment (usually air), the optically thinner medium.The fraction of the radiation that passes through the air gap can bereflected from the downstream reflector film. A large proportion of theradiation striking the lateral faces of the base body can therefore bereflected, and the radiation can, on the whole, be guided through thebase body with low losses. This preferred arrangement thereforeincreases reflectance, which has a positive effect on the illuminance ofthe optical element.

Use of the last-cited arrangement as a waveguide can be made, forexample, in connection with the visualization of data in mobile andportable electronic devices, where flat panel display technology plays amajor role. Flat panel displays can be implemented as liquid crystaldisplays (LC displays). This technology is distinguished by low-costproducibility, low electric power consumption, low weight and low spaceconsumption. LC displays are not self-emitting, however, and thereforerequire backlighting, which can be optimally implemented for example bymeans of the invention, which is distinguished by the high luminance ofthe optical element. One advantage of this type of implementation is theuse of passive elements, for example a film/air gap/reflector filmarrangement, to increase reflectance, as opposed to the use ofadditional active elements, for example LEDs, which would requireadditional energy.

In the production of an optical element, in the context of the inventionthe film is first placed in an injection mold. A filler material is thenfed into the injection mold, for example by means of an injectionnozzle, an intimate connection being formed between the filler materialand the film. The base body is fabricated from the filler material,which is preferably a transparent material. However, it is alsoconceivable for the filler material to contain particles, for examplefor scattering or wavelength-converting the radiation.

The optical element is taken out of the mold as soon as the moldingmaterial has cooled down to sufficient demoldability, whichadvantageously can take place without any significant idle time afterproduction.

Further features, advantages and improvements of an optical element willemerge from the following exemplary embodiments, described inconjunction with FIGS. 1 to 3.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective side view of a first exemplary embodiment of anoptical element,

FIG. 2 a is a perspective sectional view of a second exemplaryembodiment of an optical element,

FIG. 2 b is a perspective side view of a third exemplary embodiment ofan optical element,

FIG. 3 is a perspective side view of a fourth exemplary embodiment of anoptical element.

DETAILED DESCRIPTION

In the exemplary embodiments and figures, like or like-acting elementsare provided with the same respective reference numerals.

A first exemplary embodiment of an optical element 1 is illustratedschematically in FIG. 1. The optical element 1 is configured here as aflat, plate-shaped waveguide. The waveguide comprises a base body 2 anda film 3. The base body 2 preferably contains a transparent material,for example an epoxy resin, an acrylic resin, a silicone resin or amixture of these resins. It is also conceivable for the material tocontain particles, for example dyestuffs for changing the wavelength ofthe radiation 5 coupled into the base body.

The film 3 is particularly preferably made of an at least partiallytransparent material. It may, for example, be provided with structurehaving the effect of a lens. It may contain dyestuffs to change thewavelength of the radiation 5. However, particles for scattering theradiation are also an option.

The electromagnetic radiation 5, preferably in the visible range, isemitted by a radiation source (not shown), preferably one or more LEDs.

The monochromatic or polychromatic electromagnetic radiation 5 iscoupled into the optical element 1 via the radiation entrance face 12and is uniformly distributed over the rectangular surface. The radiationpasses through base body 2 and film 3 and exits through radiation exitface 4, which is arranged parallel to radiation entrance face 12.Alternatively, radiation exit face 4 could be arranged perpendicularlyto the radiation entrance face, which would then be located, forexample, on the side face 8 of the base body 2. In the latterarrangement, the incoupling of the radiation would take place in thelongitudinal direction of the optical element 1.

The flat waveguide can be used, for example, to uniformly illuminate adisplay unit (not shown) disposed after the optical element 1.

In the second exemplary embodiment, depicted in FIG. 2 a, the opticalelement 1 is configured as a rope-shaped waveguide. The rope-shapedwaveguide comprises a base body 2, a film 3 and a reflector film 6,which is disposed after film 3. In sectional view, film 3 and reflectorfilm 6 surround the base body 2 in a ring- or frame-like manner.

The film 3 adheres in intimate connection to the side face 8 of basebody 2. This intimate connection is created merely by back-injecting thefilm 3 with a, for example, transparent material from which the basebody 2 is formed, and advantageously requires no adhesion-promotinginterlayer between the film 3 and the base body.

The reflector film 6 is disposed after film 3, and specifically isplaced on film 3 without strengthening the adhesion, due to the forcesacting between the two films. In this type of arrangement, an air gap 7is formed between the two films.

As in the first exemplary embodiment, the base body 2 preferablycontains a transparent or partially transparent material that maycomprise particles having the aforesaid effect.

A transparent or translucent material is advantageously used for thefilm 3.

The radiation 5 coming from a radiation-emitting source (not shown)crosses the rope-like waveguide and is reflected to the center of thebase body as soon as it strikes the side face 8 of the base body.

As illustrated in FIG. 2 a, the radiation can favorably be reflectedfrom two locations: from the film 3 adjoining the air gap 7 and from thereflector film 6.

Since the material of the film 3 has a higher index of refraction thanair, at the transition between the film 3 and the air gap 7, theradiation striking the film 3 at an angle 10 equal to or greater thanthe angle of total reflection can be totally reflected (totallyreflected radiation 9).

The fraction of the radiation that strikes the film 3 at a smaller anglethan the angle of total reflection may be partially reflected by thefilm 3 or may pass through the air gap 7. The fraction of the radiationthat radiates through the film 3 can be reflected by the reflector film6 disposed thereafter (reflected radiation 11).

All in all, a high reflectance can thus be obtained by means of thetwo-layer film arrangement.

The electromagnetic radiation 5 is guided by the waveguide and extractedfrom the waveguide via radiation exit face 4.

A third exemplary embodiment of an optical element 1 is illustrated inFIG. 2 b. The optical element 1 is configured here as a flat,plate-shaped waveguide. The waveguide comprises a base body 2 and atleast two films. Film 3 and reflector film 6 are disposed on the sideopposite radiation exit face 4. As in the second exemplary embodiment,there is an air gap 7 between these two films. The same physicalconditions hold true with regard to the reflection of the radiation fromthe films.

A beam path is illustrated by way of example. The electromagneticradiation 5 is coupled into the optical element 1 through radiationentrance face 12. The electromagnetic radiation 5 radiates through thebase body 2. Radiation striking the film 3 at an angle 10 equal to orgreater than the angle of total reflection is totally reflected. Thetotally reflected radiation can further strike a side face 8 and bereflected again before exiting the optical element 1 at radiation exitface 4.

In a preferred exemplary embodiment, a film and a reflector film with anair gap between them are additionally disposed on one or more side faces(this arrangement not shown), such that the radiation striking the sideface 8 at an angle equal to or greater than the angle of totalreflection is totally reflected.

In addition, an optically active film can also be disposed on theradiation entrance face (this arrangement not shown).

All in all, a uniform reflectance can thus be obtained by means of thetwo-layer film arrangement.

FIG. 3 depicts a fourth exemplary embodiment of an optical element 1. Aperspective side view of an optical element 1 is shown.

A carrier 13 comprises on its surface a base body 2 of an opticalelement in the form of a dome-shaped cap. This preferably sphericallycurved cap is covered with a film 3 that conforms in intimate connectionto the surface of the cap 11.

The carrier 13 has, for example, a cylindrical shape. It can beconfigured as a hollow metal cylinder that is filled with air in itsinterior or comprises in its interior a transparent material, forexample an epoxy resin, an acrylic resin, a silicone resin, or a mixtureof these resins, for example topped off with a reflector film at thesurface with the environment.

Electromagnetic radiation 5, preferably in the visible range, canadvantageously be guided through by means of such a carrier. The maindirection of the radiation guided through the carrier 13 in this fashionextends parallel to the outer wall of the carrier 13.

At the end of the carrier 13, the radiation strikes the base body 2.This base body 2 preferably contains a transparent material and isconfigured for example in the form of a collecting lens. The radiation 5guided through the carrier 13 can thus be given a specific shape. Forexample, a parallel ray bundle coming from the carrier and striking thecollecting lens can be focused to a point downstream of the opticalelement.

Film 3, which adheres in intimate connection to the cap 11, ispreferably an optically active film, i.e., it can be transparent orcontain particles, for example for additional beam shaping or forchanging the color of the incident radiation.

The intimate connection between the lens 3, which can also be ascattering lens, and the optically active film 3 has proven advantageousbecause it serves to prevent radiation losses that occur when the filmfor example is mounted on the base body by means of a glue.

It is understood that the features of the invention disclosed in thedescription, the drawing and the claims may be essential to theinvention both individually and in any possible combination.

What is claimed is:
 1. A method for producing an optical elementcomprising a base body, a film, and a reflector film, in which said filmis configured to adhere to said base body and to form a connection withsaid base body without using an adhesion-promoting interlayer, said filmbeing disposed between said base body and said reflector film, said filmand reflector film defining an air gap between said reflector film andsaid film, said method comprising placing the film in an injection mold,and filling the injection mold with a filler material operative to formthe base body, such that said connection is formed between said fillermaterial and said film.
 2. The method as in claim 1, wherein saidreflector film is arranged on said film with said air gap existingbetween said reflector film and said film.
 3. The method as in claim 1,wherein said filler material is a transparent material.
 4. The method asin claim 3, wherein said filler material contains at least one of thefollowing materials: an epoxy resin, acrylic resin or silicone resin. 5.The method as in claim 1, wherein the filler material contains particlesfor scattering electromagnetic radiation.
 6. The method as in claim 1,wherein said base body is produced by injection molding.
 7. The methodas in claim 1, wherein said film is transparent or translucent.
 8. Themethod as in claim 1, wherein said film contains particles forscattering electromagnetic radiation.
 9. The method as in claim 1,wherein said film contains a phosphor.
 10. The method as in claim 1,wherein said film has a non-smooth structure.
 11. The method as in claim1, wherein said film is arranged such that it completely surrounds saidbase body in at least one cross section.
 12. The method as in claim 1,wherein said reflector film is arranged such that it completelysurrounds said base body in at least one cross section.
 13. The methodas in claim 1, wherein said optical element is configured as awaveguide.
 14. The method as in claim 13, wherein the waveguide isconfigured in a rope-shaped manner.